In semiconductor technology, due to its characteristics, III-V semiconductor compounds are used to form various integrated circuit devices, such as high power field-effect transistors, high frequency transistors, or high electron mobility transistors (HEMTs). HEMT is a field effect transistor incorporating a junction between two materials with different band gaps (i.e., a heterojunction) as the channel instead of a doped region, as is generally the case for MOSFET. HEMTs have a number of attractive properties including high electron mobility and the ability to transmit signals at high frequency, etc.
Despite the attractive properties noted above, a number of challenges known to the applicants exist in connection with developing III-V semiconductor compounds based devices. For example, it may be difficult to grow high quality gallium nitride materials on certain substrates, particularly silicon, due to property differences (e.g., lattice constant and thermal expansion coefficient) between the gallium nitride material and the substrate material. Also, it has been challenging to form gallium nitride material devices meeting the property requirements for certain applications.